The proposed research aims to determine the cellular mechanisms by which the synthesis of extracellular materials is regulated and the functions of extracellular materials in normal developmental processes. Cell cultures of chick chondrocytes are being used as a model system to study feedback regulatory mechanisms involved in the control of matrix production. The experimental approach involves the use of several environmental agents, such as conditioned medium from cartilage cell cultures and other extracellular materials, as tools to study regulatory steps in the production of specific components of cartilage matrix. Some of the same materials present in cartilage matrix are also found in early embryos. Studies are underway on the possible functions of thes extracellular materials. BIBLIOGRAPHIC REFERENCES: Morriss, G.M. and Solursh, M. 1976. Cephalic neural fold development in rat embryos. J. Anat. (in press-abstract). Fisher, M. and Solursh, M. 1976. Identification of hyaluronic acid in primary mesenchyme of chick embryos and evidence concerning its developmental significance. J. Cell Biol. (in press-abstract).